Nonlinear phenomena are a very important topic of modern physics that is usually taught only at an advanced level. An elementary introduction of this subject is presented, considering nonlinear waves in shallow water. The Korteweg–De Vries equation is derived by means of simple physical arguments, and the approximations involved are discussed. Solutions that propagate without changing their shape are studied and their properties are described using an analogy with a mechanical oscillator. The solitary and cnoidal waves are obtained as well as harmonic waves as a limiting case. The mathematics employed is simple and straightforward.

The claims for parallels between modern physics and Eastern mysticism are critically examined in view of their possible educational impact. The overall nature, as well as specific examples of parallelism, are considered in order to emphasize the problems faced in trying to maintain the validity of such claims. The role of analogies within physics is briefly discussed.

In a squeezed state, the variance in one canonical variable may be suppressed below that normally associated with either the ground state or a coherent state, at the expense of an expansion in the variance of the conjugate variable. Squeezed states are usually discussed in the context of quantized light fields. The principal properties of squeezed states are demonstrated using the motion of quantum mechanical simple harmonic oscillators. The motion of a single oscillator is discussed to introduce the key concepts of squeezing, including quadrature operators, and the error contours of the Wigner function describing the quantum quasiprobability distributions in phase space of the oscillator motion. The main topic of two‐mode squeezing is then addressed, in which the fluctuations in a system of two oscillators are tightly correlated. The existence of squeezing is demonstrated in normal mode coordinates representing motion of superpositions of the motion of the two oscillators. The fluctuations within a single oscillator are shown to increase when squeezing increases in the normal modes, generating thermal noise in individual mode subsystems.

The least‐squares method of curve fitting may be posed as a problem in Newtonian mechanics for a fictitious particle. By assuming fictitious time dependence for the fitting parameters, Newtonian equations of motion (EOM) for the particle are obtained. In one technique, dynamic simulated annealing(DSA), the EOM are second order in time and, in another, steepest descents (SD), they are first order due to the presence of damping. These EOM’s are solved to perform Gaussian fits to singly peaked and doubly peaked data. Generalization to many‐peaked data, as occur frequently in spectroscopy, is straightforward.

Two formulations of the empirical principles on which classical dynamics is founded are presented and compared. The first is based on the law of conservation of momentum and gives initial priority to the concept of mass. The second is based on Newton’s laws and gives initial priority to the concept of force. On the basis of a variety of criteria the first formulation is shown to be superior to the second.

By introducing the electromagnetic field in the customary way, ideas are promoted that do not correspond to those of contemporary physics: on the one hand, ideas that stem from pre‐Maxwellian times when interactions were still conceived as actions at a distance and, on the other hand, ideas that can be understood only from the point of view that the electromagnetic field is carried by a medium. A part of a course in electromagnetism is sketched in which, from the beginning, the electromagnetic field is presented as a system in its own right and the local quantities energy density and stress are put into the foreground. In this way, justice is done to the views of modern physics and, moreover, the field becomes conceptually simpler.

The Feynman propagator is expanded in the adiabatic limit, wherein the time scale over which the potential varies is long compared to typical quantum mechanical oscillation times in the problem. Comparison with known exact results is made for two simple models.

A pedagogically pleasing and mnemonically useful method for expressing the velocity and acceleration vectors in orthogonal systems of coordinates is shown. The method relies on expressing the time derivatives of the unit vectors in matrix form. It is also noted that the spatial derivatives of the unit vectors obey a similar rule.

Magnetic forces are sometimes viewed as being due to tension in the field lines or mutual repulsion of field lines. The validity of these concepts is examined by considering the stresses acting on a straight, current‐carrying conductor in a uniform magnetic field.

An understanding of two‐dimensional crystallography calls for a knowledge of the four basic isometries of the Euclidean plane (reflections, translations, rotations, and glide reflections) and the ability to combine any two of these to obtain a third. After a review of how the other isometries can be expressed in terms of reflections, an algebra and geometry of mirror operations (reflections) is introduced that permits a straightforward evaluation of the product of an arbitrary number of plane isometries.

One‐dimensional scattering of a particle or a wave packet by a finite number of periodic potential barriers is studied. The fundamental physical mechanism that determines the transmission coefficient is shown to be quantum interference between waves with different numbers of inner reflections. The tendency of the transmission coefficient to saturate with respect to an increase in the number of barriers is due to the free‐particle nature of a particle subject to a completely periodic potential.

A general expression is found for the magnetic field generated by a long rectilinear current placed in a static background gravitational field. Then it is applied to the case of uniform, Schwarzschild, general Reissner–Nordstrom and ‘‘charge‐equal‐to‐mass’’ Reissner–Nordstrom background metrics. All the calculations are very simple and can easily be done in the classroom.

The possibility is suggested of using charts of modulus and phase of the S matrix to illustrate lessons on nonrelativistic scattering in quantum mechanics courses. Special attention is paid to the existence of resonances and to Levinson’s theorem on the number of bound states.

In this article computer‐aided experimentation means using the microcomputer as a laboratory instrument emulator, data logger, and analyzer in an experiment. Through an inexpensive, yet versatile experiment involving an RLC circuit, this article describes how to use the microcomputer as a pulse generator/voltage source, a digital oscilloscope, an ac voltmeter, a frequency meter, and a data logger and analyzer by investigating its time‐ and frequency‐domain behavior. Excellent agreement is found between experiment and theory, which validates the measurement, hardware, and software techniques used. A new and accurate method for characterizing L and C at the natural frequencies of the RLC circuit is also presented.

Can the anthropic principle be used to understand the values of the fundamental constants of nature and, conversely, can the existence of life be said to arise from a remarkable feat of fine tuning on the part of the cosmos? The conditions required for the existence of life that depend upon stellar, atomic, and molecular structure are focused on and the degree to which these conditions would have been met had the fundamental constants been different from their known values is analyzed. The tentative answer to both questions is no.